MAIN AIM OF THE STUDY To establish whether hemodynamic management guided by the hypotension prediction index (HPI) guided by the administration of intravenous fluids and vasoactive drugs in patients undergoing elective major abdominal surgery reduces the incidence of postoperative moderate-severe acute kidney injury (AKI) in the 30 days after surgery.

STUDY DESIGN A low intervention level clinical, blinded, controlled, randomized, multicenter, with daily follow-up of patients until hospital discharge and of postoperative complications and mortality 30 days after surgery will be performed.

This is a low-intervention clinical trial comparing standard treatments:

• The drugs used in the investigation are licensed.
• The drugs are used according to the indications contemplated in the technical data sheet and there are published scientific data on their efficacy and safety.
• The complementary diagnostic or follow-up procedures entail a very limited additional risk or burden to the safety of the subjects, which is minimal compared to that of standard clinical practice.

STUDY DISEASE Intraoperative hemodynamic monitoring and management in surgical patients undergoing major abdominal surgery.

STUDY POPULATION AND TOTAL NUMBER OF PATIENTS The sample of this study consists of patients of both genders, aged over 65 years and/or physical status ASA III or IV, undergoing elective major abdominal surgery (abdominal, urological, gynecological) under general/combined anesthesia (using laparoscopic or open approaches.

To detect a 5% absolute reduction (from 10% to 5%) in the primary outcome variable (postoperative AKI up to 30 days) with a sample size ratio of 1%, and an overall type I error rate of 5%, we need 870 patients (435 per arm). Assuming a 10% loss rate, the total amounts to 958 patients, 479 for each group.

DURATION OF THE STUDY The total planned duration of the overall study, which includes authorization, recruitment of subjects, and follow-up of subjects until completion of the analysis of the results obtained, is 19 months.

Inclusion Criteria:

• Patients over 65 years of age and/or physical condition ASA III or IV.
• Patients who have major elective abdominal surgery indicated: general surgery, urology, gynecology, by laparoscopic or open approaches.
• Patients who sign the informed consent, agreeing to participate in the study.

Exclusion Criteria:

• Stage 4 or 5 chronic kidney disease (eGFR < 15 ml/ min)
• Renal transplantation in the previous 12 months
• Glomerulonephritis, interstitial nephritis or vasculitis
• Anuria at inclusion
• Pre-existing AKI
• Renal replacement therapy (RRT) in the last 90 days
• Indication for renal replacement at the time of inclusion
• Participation in another interventional trial investigating a drug/intervention affecting renal function
• Patients with atrial fibrillation
• Patients with known cardiac shunts.
• Patients whose surgical indication is urgent
• Pregnancy or lactation
• Patients expected to die within 30 days.
• Acute myocardial ischemia within the previous 30 days.
• Acute pulmonary edema within the previous 30 days
• Any contraindication to vasoactive or inotropic medication at low doses

Upon specific request following the publication of the study

From publication on clinicaltrials.org until 1 year after publication of the results.

under request and Steering Committe review